JP2002138453A - Collapse prediction method of slope by chemical weathering of sedimentary rock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collapse prediction method of slope such as a landslide, a landslip or the like. SOLUTION: A weathering state of a bedrock and an activity of landslide or the like are predicted on the basis of an elution test of a bedrock sample or an analytical result of a quality test of ground water from composition to be eluted and its variations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prediction of slope failure such as landslide or landslide.

[0002]

2. Description of the Related Art There is a proverb that a disaster will come when it is forgotten. However, if a disaster can be predicted, everyone wishes, not just those who are involved in the disaster.

Conventional methods for predicting the occurrence and continuation of slope failures such as landslides include geotechnical methods such as topographic analysis, survey drilling, in-situ testing, observation of artificial seismic waves, rock and soil testing, and the present invention. There are chemical methods for analyzing water quality, composition of rocks, earth and sand, and X-ray diffraction of clay minerals, which are employed in the present invention.

[0004]

The cause of the occurrence of landslides and slope failures is a decrease in the strength of the ground due to the progress of weathering of the rocks. That is, weathering is an increase in the porosity of the ground, which is caused by sedimentation and clayification, and the result is a decrease in the strength of the ground. Weathering can be physical or biochemical, but they promote each other. However, weathering at a deep depth from the surface is mainly affected by chemical weathering because it is not easily affected by the outside air. Its biochemical weathering is mainly a reaction with groundwater.
Component is generally constituting the rock, as a result biochemical _{reactions, Cl · SO 4 · Na ·} Mg · Ca · K · SiO 2
· _Fe is said to dissolve in 2 _O 3 of · _Al 2 _{O 3} sequence.

[0005] In recent years, chemical changes in the constituents of sedimentary rocks,
Research on the relationship between weathering has been pursued. The results of the study are as follows. Due to the progress of weathering, there is a decrease in all the constituents and especially the disappearance of Ca and Na contents. There is a case where the Ca content increases when weathering. In addition, the change from Na-type smectite to type-smectite, and the ground strength is reduced. Fresh rock was powdered, Ca content was added, and the unit volume and water content were adjusted to conduct a shear test. However, the strength decreased. However, they are abstract and their chemical proof is not clear.

[0006]

In order to solve the above-mentioned problems, the present invention has conducted researches such as experiments for many years, and clarified weathering, landslides and slope failures from a chemical direction. The tests and analyzes performed to achieve the objectives were carried out by dissolution tests in addition to the conventional methods. The samples used to determine the weathering state of the ground are fresh rock, weathered or sedimented rock, slip surface clay, groundwater near the borehole borehole surface, and surface spring water.

[0007] The characteristics of the analytical results have been shown especially in dissolution tests. In the fresh part, the elution amount of Na is large and the elution amount of Ca is small. As the weathering progresses, the elution amount of the Na content decreases, and conversely, the Ca content increases. Further, as the weathering proceeds, the elution amount of both Na and Ca decreases and disappears.

[0008] This phenomenon is the same with other components. Each component in the ground reacts with and elutes with the groundwater, and remains there or dissolves in the groundwater and flows downstream. It accumulates once in the voids and on the sliding clay. As such, all the components gradually flow out and reduce the voids.

Further, Na elutes at an early stage and replaces Ca eluted later. Then, the Ca content increases in volume and expands. That is, a decrease in the shear strength of weathered rock and slip surface clay results in a decrease in the result of this chemical reaction. And the landslide continues while these are repeated.

[0010] Changes in these components naturally appear in groundwater.

From the above, landslides and slope failures can be predicted from the results of the dissolution test and the groundwater quality test. One is when the ground is weathered and the amount of Ca eluted increases in place of Na. One is when the Ca content shows the maximum elution amount. One is when each component disappears.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The prediction of occurrence of landslides and slope failures aimed at by the present invention will be described with reference to the drawings. In order to grasp and compare the present ground conditions, fresh rock, weathered or sedimented rock, slip surface clay, groundwater near the slip surface in the borehole and spring water on the surface were collected. Know the state. Next, from the results of the composition analysis of the ground sample, the analysis of the dissolution test, and the water quality analysis, the chemical weathering state is known from the composition ratio and the elution amount of the ground component, and the water quality. The prediction of the occurrence of landslides and slope failures is performed by plotting the results of the dissolution test and the analysis of water quality on the ground conditions in FIG. 1 and the relationship between Na and Ca.

In the fresh part (C) where the ground is not weathered, the elution amount of Na is large and the elution amount of Ca is small (1). Weathered part (B) where weathering has progressed
Then, the elution amounts of the Na component and the Ca component are reversed, and the elution amount of the Na component decreases and the Ca component increases, so that the position (3) is reached. Further, in the strongly weathered part (A) where weathering has progressed, N
Both the a and Ca components are at the position (5) where the elution amount decreases and disappears. And the landslide continues while these are repeated.

The prediction of landslides and slope failures is performed based on the results of the dissolution test of ground samples and the analysis of groundwater quality. One is the point of time (2) where the ground has weathered and the amount of Ca eluted begins to increase in place of Na. One is the time point (3) where the Ca content shows the maximum elution amount. One is that each component disappears (4)-
(5) It is time. They also ensure that the slippage is even faster when the conditions of rising groundwater are added. In other words, when the amount of Ca elution increases (2) or more, the landslide is in an environmental condition in which it slides. In the case of (3) in which the Ca content indicates the maximum elution amount, the landslide is already in the sliding phase. In addition, in the case of (5) in which the amount of elution decreases and disappears for both Na and Ca, there are many voids when the nature such as the rise of groundwater is uniform, so there is a condition that the ground can slide at any time.

This phenomenon is the same as for other components. Each component in the ground reacts with and elutes with the groundwater and remains there, or dissolves in the groundwater and is particularly weathered in other places. It accumulates on sliding clay and accumulates once. As such, the components flow out and decrease gradually, increasing the voids.

In the case of the condition (2), which has not yet been slid, the groundwater is regularly sampled and the water quality is analyzed and monitoring is continued. When the amount of Ca eluted increases, detailed investigation and monitoring are performed.

[0017]

The method for predicting landslides and slope failures according to the present invention detects the elution of the constituents of the ground, that is, weathering, by a chemical method, and in particular, landslides from the relationship with Na and Ca contents. Can be predicted. In addition, there is also a difference in convenience, such as monitoring the spring water quality on a regular basis so that it can be easily monitored.

[0018]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of the present invention during mortar injection.

[Explanation of symbols]

1 The position where the amount of Na eluted is large and the amount of Ca eluted is small 2 The position where the amount of Ca eluted increases 3 The position where the Ca elutes the maximum eluted 4 The position where Ca is reduced 5 The Na and Ca both Location where elution disappears or is close to it A Fresh part B Weathered part C Strong weathered part

Claims (3)

[Claims] 1. Prediction of landslides and slope failures is carried out from the results of the dissolution test of ground samples and the results of groundwater analysis. One is the point of time (2) where the ground has weathered and the amount of Ca eluted begins to increase in place of Na. One is the time point (3) where the Ca content shows the maximum elution amount. One is that each component disappears (4)-
(5) It is time. They also ensure that the slippage is faster and faster when the conditions of rising groundwater are added. 2. The phenomenon is the same with other components. Each component in the ground reacts with and elutes with the groundwater, and remains there, or dissolves in the groundwater, and especially in the weathered voids of other places. And accumulates once on the sliding clay. As such, the components flow out and decrease gradually, increasing the voids. (3) In the case of the condition (2), which has not yet been slid, the groundwater is regularly collected and the water quality is analyzed and monitoring is continued. When the amount of Ca eluted increases, detailed investigation and monitoring are performed.